zinostatin and Melanoma

Mechanisms underlying radiation and chemotherapy resistance, the hallmark of human melanoma, are not well understood. Here we demonstrate that expression levels of signal adaptor protein TRAF2 coincide with melanoma resistance to UV-irradiation. Altered TRAF2 signaling by a form of TRAF2, which lacks the ring finger domain (TRAF2DeltaN), increases activities of p38 MAPK, ATF2, and the level of TNFalpha expression. Forced expression of TRAF2DeltaN in HHMSX highly metastatic melanoma cells that lack Fas expression and thus utilize the TNFalpha-TNFR1 as the major apoptotic pathway sensitized cells to UV-induced apoptosis. An over twofold increase in degree of apoptosis was observed in TRAF2DeltaN expressing cells that were treated with actinomycin D, anisomycin or with the radiomimetic drug neocarzinostatin. Sensitization by TRAF2DeltaN is selective since it was not observed in response to either Taxol or cis-platinum treatment. TRAF2DeltaN effects are primarily mediated via p38 since inhibition of p38 reduces, whereas activation of p38 promotes the level of UV-induced apoptosis. Conversely, activation of IKK attenuates the sensitization of melanoma by TRAF2DeltaN, indicating that p38-mediated suppression of NF-kappaB activity is among TRAF2DeltaN effects. Our finding identifies p38, TNFalpha and NF-kappaB among key players that efficiently sensitizes melanoma cells to UV-, ribotoxic (anisomycin) and radiomimetic chemicals-induced programmed cell death in response to aberrant TRAF2 signaling.

Topics: Acetyltransferases; Anisomycin; Apoptosis; Dactinomycin; Gene Expression Regulation, Neoplastic; Humans; Melanoma; Mitogen-Activated Protein Kinases; NF-kappa B; p38 Mitogen-Activated Protein Kinases; Protein Biosynthesis; Proteins; Radiation Tolerance; TNF Receptor-Associated Factor 2; Tumor Necrosis Factor-alpha; Up-Regulation; Zinostatin

Monoclonal antibodies (IgG1) against high molecular weight antigen A-1-43 on human melanoma cell line A-375 were successfully linked to the anti-tumour protein neocarzinostatin (NCS) using the heterobifunctional reagent N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP). The conjugate retained both the reactivity of the antibody and the toxicity of the drug. The antigen-bearing cell line A-375, antigen-lacking cell line MeWo and normal skin fibroblasts were exposed to NCS-monoclonal antibody conjugates. As negative control, cells were also treated with free NCS and NCS coupled to normal mouse IgG1 antibodies. Inhibition of 3H-thymidine uptake after treatment was used to measure the biological activity of the cytotoxic drug complex or substance, respectively. Comparing the inhibition dose for 50% uptake (ID50) it was found that the monoclonal antibody-drug complex is about 100 times more toxic for the antigen-bearing cell line than free NCS or normal mouse IgG1-NCS. This high toxicity is due to a local increase of drug concentration on these cells. With the two cell lines lacking the appropriate antigen no significant differences in the ID50 values were observed. A selectivity factor of 40-50 was obtained by comparing the cytotoxic effect of the monoclonal antibody-NCS conjugate upon the antigen-bearing as opposed to the antigen-lacking cell type. These data demonstrate, that the toxicity of NCS can be directed by monoclonal antibodies to human tumour cells carrying the corresponding surface antigen.

Topics: Antibiotics, Antineoplastic; Antibodies, Monoclonal; Cell Division; Cross-Linking Reagents; Humans; Immunoglobulin G; Immunotherapy; Melanoma; Zinostatin

One hundred twenty-two patients with disseminated malignant melanoma were randomized using an unbalanced randomization to receive chlorozotocin, neocarzinostatin, or MeCCNU. Of the 114 evaluable patients, 46 received chlorozotocin, 47 received neocarzinostatin, and 21 received MeCCNU. The response rates to these three drugs were 9%, 4%, and 14% respectively. Median survival times were 4.2, 3.4, and 5.8 months respectively. Toxicity was acceptable with all three agents. Chlorozotocin and neocarzinostatin do not appear to offer any improved response rates over MeCCNU for patients with disseminated malignant melanoma.

Topics: Adult; Aged; Antineoplastic Agents; Female; Humans; Male; Melanoma; Middle Aged; Neoplasm Metastasis; Nitrosourea Compounds; Random Allocation; Semustine; Skin Neoplasms; Streptozocin; Zinostatin